The liver microsomal fractions of seven mammalian species including rat, do
g, monkey, hamster, mouse, gerbil and humans, catalyzed the hydroxylation o
f saturated (lauric, myristic and palmitic) and unsaturated (oleic and lino
leic) fatty acids to the corresponding omega and (omega-1)-hydroxylated der
ivatives, while stearic acid was not metabolized. Lauric acid was the most
efficiently hydroxylated, and the rank of catalytic activity was lauric > m
yristic > oleic > palmitic > linoleic. Among the mammalian species studied,
mouse and hamster presented the highest level of fatty acid omega and (ome
ga-1)-hydroxylases, while the lowest activity was observed in dog and monke
y. In all the animal species, the (omega-1)-hydroxylation of fatty acids co
rrelated significantly with the immunodetectable content of CYP2E1 and the
4-nitrophenol hydroxylation activity, known to be mediated by cytochrome P4
50 2E1. On the contrary, only the omega-hydroxylation of lauric acid slighl
y correlated with the level of cytochrome P450 4A, while no significant cor
relation was found with the omega-hydroxylation of the other fatty acids. F
urthermore, chemical and immune-inhibitions of the hydroxylations of fatty
acids led to the conclusion that fatty acid (omega-1)-hydroxylase activity
is catalyzed by P450 2E1 in all the mammalian species, while the fatty acid
omega-hydroxylase activity may be catalyzed by cytochromes P450 from the 4
A family. Therefore, lauric acid (omega-1)-hydroxylation along with 4-nitro
phenol hydroxylation can be used as a specific and sensitive method to meas
ure the level of CYP2E1 induction in humans and various animals. (C) 1999 E
lsevier Science Ireland Ltd. All rights reserved.